(1) Field of the Invention
The present invention relates to a surveillance image retrieval apparatus that searches surveillance images for human face images. The present invention also relates to a surveillance system equipped with the above-mentioned surveillance image retrieval apparatus.
(2) Description of the Related Art
When a face image is used to search surveillance images for a person, a list of face images or frame images appears on a display as a search result. A surveillant, who monitors the surveillance images, views the list displayed as the search result to verify whether the search result really indicates a targeted person. Images presented to the surveillant as the search result are not always appropriate for visual confirmation. More specifically, the face images presented as the search result may occasionally be small in size, obtained obliquely, or otherwise unsuitable for personal identification.
An optimum face image recorder disclosed in Japanese Patent Application Laid-Open publication No. 2005-227957 selects the most objectively balanced frontal face image from a series of successive surveillance images and stores the selected face image in a database. When the surveillance images include face images that are obtained within a certain period of time, the optimum face image recorder concludes that the face images represent the same face, selects the best-shot face image from them by a predetermined evaluation method, and records the selected best-shot face image. When the database for the optimum face image recorder is used to conduct a person search, only the best-shot image is selected as the result of the search. Consequently, a list of images obtained is readily used by a surveillant for visual confirmation purposes.